1. Technical Field
The present invention relates to a horizontal articulated robot equipped with an angular velocity sensor, and a method of controlling the horizontal articulated robot.
2. Related Art
In the past, there has been known a horizontal articulated robot which performs damping control of the arm using an angular velocity sensor for detecting the angular velocity of the arm as described in JP-A-2005-242794 (Document 1). A first arm is coupled to a base of the horizontal articulated robot described in Document 1 so as to be able to rotate with respect to the base, and a second arm is coupled to the tip of the first arm so as to be able to rotate with respect to the first arm. Further, when the first arm rotates due to the drive force of a first drive source, the rotational angle of the first arm is detected by a first angle sensor for detecting the rotational angle of the first drive source, and the angular velocity of the first arm with respect to the base is detected by a first angular velocity sensor mounted on the first arm. On this occasion, in the robot controller for controlling the driving procedure of the first drive source, feedback control is performed on the first drive source based on the data detected by the first angle sensor and the first angular velocity sensor so that the data to be detected become equal to predetermined values.
Further, when the second arm rotates due to the drive force of a second drive source, the rotational angle of the second arm is detected by a second angle sensor for detecting the rotational angle of the second drive source, and the angular velocity of the second arm with respect to the base is detected by a second angular velocity sensor mounted on the second arm. On this occasion, in the robot controller described above, feedback control is performed on the second drive source based on the data detected by the second angle sensor and the second angular velocity sensor so that the data to be detected become equal to predetermined values similarly to the control procedure with respect to the first drive source. Thus, the damping control of the first and second arms is performed.
Incidentally, in order to drive the angular velocity sensors described above, it becomes necessary to connect a variety of electric wires such as wires for supplying the angular velocity sensors with electricity or wires for transmitting the detection signals of the angular velocity sensors between the angular velocity sensors and the controller. Such electric wires are also required for the drive sources besides the angular velocity sensors, and are generally connected to an external controller through a hollow substrate. Therefore, in the case of respectively disposing the angular velocity sensors to the first and second arms as in the case of the horizontal articulated robot described above, the same number of electric wires as the number of angular velocity sensors are required. As a result, the work of laying the electric wires for the angular velocity sensors around becomes cumbersome.
Incidentally, the vibration caused in the first arm is generally amplified by another arm coupled to the first arm, and then reaches an end effector of the horizontal articulated robot. Therefore, it is true that it is also possible to reluctantly omit the second angle sensor and the second angular velocity sensor described above, and at the same time perform only the damping control of the first drive source based on the detection result of the first angular velocity sensor to thereby suppress the vibration of the end effector. However, the track drawn by the first arm with respect to the base generally includes a larger number of tracks with small curvature compared to the tracks drawn by other arms with respect to the base. Therefore, the chances of folding the electric wires drawn from the first arm increase, and further, the curvature in the folded portions also becomes smaller compared to the electric wires drawn from other arms. Therefore, since the electric wires connected to the first angular velocity sensor are required to have higher durability than the electric wires connected to the second angular velocity sensor, after all, it results that restrictions related to the layout of such electric wires and cumbersomeness of laying the electric wires around still remain.